Various mechanisms and systems exist to determine topography and respective changes therein with respect to surfaces. An example-system 100 known in the art for determining geometry of a curved smooth-specular surface 102 is illustrated in FIG. 1. The constituent-components of the system 100 include a light-source array 104, and a camera 106. An optical-ray 108 emitted from light source array 104 impinges curved surface 102 in point 110, and becomes reflected in form of the ray 112. The position in space of the ray 112 is determined by the camera 106.
When position of the point 114 is known and the position of the point 110 at which ray 203 is impinging measured curved surface 204 in terms of a coordinate (say z coordinate of a cartesian coordinate system acting as frame of reference) is known, then a local 3D slope of the smooth surface, or equivalently one or more parameters describing a plane 116 which is tangential to the curved-surface 102 may be determined.
In some instances, with respect to the system 100, in order to determine parameters of the plane 116, an exact position of the point 114 (e.g., position in three-dimensional space) may need to be established. This may be performed using a flat-mirror 202 as shown in FIG. 2. The flat-mirror 202 is placed at in a position approximating position of the curved-surface 104 shown in FIG. 2. The position of the ray emanating from point 114 is measured for two different positions of the mirror 202 separated by known distance H. As may be understood by a person skilled in the art, such measurement uniquely determines position of the point 114 in three-dimensional space or in other words, an object-space position of plurality of LEDs or any other light emitting source.
Yet, in order to measure object space position of a plurality of the light emitting devices (LED) residing on the light source array 104, one may need to properly identify which image of the LED corresponds to which LED within the light source array 104. In other words, there may be a requirement that LEDs captured in the image need to be mapped with the actual LEDs as present within the array 104.
In an operation as associated with FIG. 2, when the plurality of LEDs residing on the light source array 104 are simultaneously energized, the camera 106 records a plurality of spots corresponding to different LEDs within the image. When the height ‘H’ of the mirror 202 changes, the positions of light-spots observed by the camera 106 move as well within the image generated by the camera 106. If the magnitude of H is large, such movement may be also large with comparison to spacing between LEDs within the light source array 104. In order to properly determine object-space coordinates for the point 114, it may thereby be necessary to properly identify which LED in the array 104 corresponds to which spot or point observed at the focal-plane of the camera 106 and reproduced within the image.
At least in order to enable identification of the LEDs from the captured and electronically generated images, one could in principle energize only one LED at the time and perform measurements as described in FIG. 2 while having one LED illuminated at particular instant of the time. However, owing to a fact that the array of LEDs 104 may contain large number of LEDs (e.g., ranging from 104 to 107), the measurement of curved surfaces may require a large amount of time also (e.g., time of the order of 104-108 seconds in some instances) or may take a substantial number of hours to perform. Accordingly, the approach of performing measurements based on illumination of individual LEDs is impractical and proves burdensome in long run.